millwood
Advanced Member level 3
matrix leds
I thought about ways to drive the most number of LEDs with a given number of pins from a mcu (a PIC in this case).
you can drive two LEDs from one pin - but one of the LEDs has to be on at a given point.
you can drive two LEDs from two pins - you can put both of them off.
with three pins, you can connect two LEDs, reverse biased, between any two pins so you can drive a total of 6 LEDs. However, you have to turn any pin that you are not using into a high impedance mode (input).
so here is a little program that demonstrates that concept. it runs on a 12f675, using three pins to drive six LEDs.
you can easily expand the program so that it can drive n*(n-1) LEDs using n pins.
I thought about ways to drive the most number of LEDs with a given number of pins from a mcu (a PIC in this case).
you can drive two LEDs from one pin - but one of the LEDs has to be on at a given point.
you can drive two LEDs from two pins - you can put both of them off.
with three pins, you can connect two LEDs, reverse biased, between any two pins so you can drive a total of 6 LEDs. However, you have to turn any pin that you are not using into a high impedance mode (input).
so here is a little program that demonstrates that concept. it runs on a 12f675, using three pins to drive six LEDs.
Code:
#include <htc.h>
#define COMBO 6
#define LEDPort GPIO
unsigned char LEDArray[COMBO][2] = {//first byte for trisio and 2nd byte for port
{0b100, 0b001}, //pin0//1 output, pin0 high pin1 low
{0b010, 0b001}, //pin0//2 output, pin0 high pin2 low
{0b100, 0b010}, //pin0//1 output, pin0 low pin1 high
{0b001, 0b010},
{0b010, 0b100},
{0b001, 0b100}
};
void delay(unsigned long int dly) {
for (; dly>0; dly--)
;
}
__CONFIG(MCLRDIS & WDTDIS);
void
main(void)
{
unsigned char i;
CMCON=0x07;
ANSEL=0x00;
while (1){
//TODO Auto-generated main function
for (i=0; i<COMBO; i++) {
TRISIO=LEDArray[i][0];
LEDPort=LEDArray[i][1];
delay(20000);
}
}
}you can easily expand the program so that it can drive n*(n-1) LEDs using n pins.